1. Field of the Invention
The present invention relates to an optical fiber array block and, more particularly, to an optical fiber array block embedding optical devices such as photodiodes for use in a monitor.
2. Description of the Related Art
Optical circuit devices are widely used in a wavelength division multiplexing (WDM) optical communication system. The optical circuit devices include an arrayed wavelength grating (AWG) device, an arrayed variable optical attenuator (VOA), and so forth. When a WDM optical communication apparatus is practically used in an optical communication system, the intensity of an optical signal transmitted between optical circuit devices is generally varied at each optical fiber channel due to insertion loss resulting from an optical coupling characteristic of each channel, optical wavelength amplifying characteristics, and an optical transmission path difference. In the optical communication system, it is significant that different-intensity optical signals are readjusted to have the uniform intensity so as to correctly transmit the optical signals to multiple channels. For that reason, what is firstly needed is to accurately measure the different intensities of the optical signals.
There are various approaches to measure the intensity of an optical signal in each channel. One of the various approaches is explained with reference to FIG. 1.
As shown in FIG. 1, a tap coupler 15 for dividing an optical signal at a constant ratio is coupled to each optical fiber 13 from an optical circuit device 10 with a horizontal waveguide integrated therein and an optical fiber array block 11. As a light receiving element, a monitor photodiode 19 for detecting the intensity of an optical signal is optically coupled to one end of an optical line 17 branched by a tap coupler 15. The optical signal detected from the photodiode 19 generates photocurrent having a functional relation to the intensity thereof, and is inputted to a control module 23 via an electric wire 21. The optical signal processed in the control module 23 is feedbacked to a controller of the optical circuit device 10 of a previous stage when an optical signal already passed, controlling an attenuation rate of the optical signal.
Unfortunately, the above-described approach encounters a problem. The problem is to necessarily to install a branch coupler and a light receiving element in each channel, and to install a control module to be transmitted to an optical circuit device of a previous stage by processing an electrical signal of the light receiving element. Further, the space for a photo wire connecting them is needed. Therefore, this approach requires a number of parts used for measuring the intensity of the optical signal throughout a number of channels. Since each of the parts has a great volume and their connection structure is very complicated, there is difficulty in integrating devices, used in this approach, in a small-sized module. In conclusion, the process for uniformly controlling the intensity of an optical signal leads to increase in the total volume of an optical communication apparatus as well as complication of a structure and a fabricating process.